In general the relatively compact type of aquarium which is used in a domestic environment has insufficient surface area to absorb enough oxygen to support a substantial number of fish. To overcome this problem, therefore, some form of aeration is required and this can be achieved by having an air pump which arranges to pump a continuous supply of air into the lower part of the aquarium so that a stream of air bubbles moves up through the water giving a good exchange of oxygen with the water. Alternatively a water pump can be provided which either sprays a jet of water onto the top surface of the water to create a ruffling of the surface and therefore improved aeration, or alternatively, by means of say a venturi effect, mixes air with a stream of water which is then ejected into the aquarium so as again to provide a stream of air bubbles.
Irrespective of the manner of aeration however, the result is that the top surface of the water is significantly disturbed. As a result it is not possible to see through the top surface clearly. This does not usually matter with traditional domestic aquaria since, generally speaking, it is intended that one views the interior of an aquarium through transparent side walls. Often the top is covered and contains equipment for aerating and filtering the water and illuminating the aquarium.
It is an object of the present invention however to enable an aquarium to be designed which can be seen through the top surface.